Multifocal ophthalmic lens

ABSTRACT

A multifocal ophthalmic lens, having outer annular zones with vision correction powers less than a far vision correction power of the patient, is disclosed. These additional annular zones come into play, when the pupil size increases under dim lighting conditions, to thereby compensate for the near-vision powered annular zones. The net effect of the additional near vision annular zones and the additional annular zones having power less than the far vision correction power is to shift the best quality image from in front of the retina to an area on the retina of the eye, to thereby reduce halo effects and improve image contrast.

FIELD OF THE INVENTION

[0001] The present invention relates generally to ophthalmic lenses and,more particularly, to a multifocal ophthalmic lens adapted forimplantation in an eye, such as an intraocular lens, or to be disposedin a cornea, such as a corneal inlay.

BACKGROUND OF THE INVENTION

[0002] The general construction of a multifocal ophthalmic lens is knownin the art. U.S. Pat. No. 5,225,858, which is incorporated herein byreference, discloses a multifocal ophthalmic lens including a centralzone circumscribed by multiple concentric, annular zones. This patentdiscloses a means of providing improved image quality and lightintensity for near images. The improved image quality is accomplished bymaintaining the near vision correction power of appropriate zones of thelens substantially constant for a major segment of the near visioncorrection power region of each zone, and by providing a central zonehaving an increased depth of focus.

[0003] The major segment of each near vision correction power region,which has a substantially constant near vision correction power,inherently reduces the depth of focus associated with far vision. Thelocation of near focus is typically immaterial for near vision, becauseof the ability of the user to easily adjust the working distance of thetarget object. The patent discloses progressive vision correction powersin the central zone for extending the depth of focus. The increaseddepth of focus provided by the central zone helps to compensate for thereduction in depth of focus associated with the near vision correctionpower regions. This feature is particularly applicable to an intraocularlens, since the patient has minimal residual accommodation, i.e., theability of a normal eye to see objects at different distances.

[0004]FIG. 1 shows how the multifocal ophthalmic lens 6 of the prior artfocuses parallel incoming light onto the retina 10 of the eye. For thenormal lighting condition with a 3 mm pupil diameter, the rays 7 passthrough a far focus region of the multifocal ophthalmic lens 6, and arefocused onto the retina 10. The rays 8 pass through a near region of themultifocal ophthalmic lens 6, and are focused into a region between theretina 10 and the multifocal ophthalmic lens 6.

[0005] The multifocal ophthalmic lens 6 shown in FIG. 1 shows thepassage of parallel rays through the multifocal ophthalmic lens 6 in awell-lit environment. In low lighting conditions, the pupil enlarges,and additional annular zones of the multifocal ophthalmic lens 6 becomeoperative to pass light therethrough. These additional annular regionsoperate to provide additional far (rays 10 in FIG. 1) and near-focuscorrective powers to the multifocal ophthalmic lens 6. Presence of theadditional intermediate and near rays shift the best image quality forfar vision to the location in front of the retina. As a result, in lowlighting conditions the best quality image of the multifocal ophthalmiclens 6 appears in a region slightly in front of the retina 7. A userlooking through the multifocal ophthalmic lens 6 while driving at night,for example, may notice an undesirable halo affect around a brightsource of light. The shift in the best quality image just in front ofthe retina 7 instead of on the retina 7 increases the halo effect makingdriving for some people difficult.

[0006] A problem has thus existed in the prior art of providing amultifocal ophthalmic lens, which can provide a desirable far visioncorrection in low lighting conditions, but which does not unnecessarilyelevate halos and contrast reductions under increased pupil size whichusually occurs in low lighting conditions. Thus, the prior art has beenunable to produce a multifocal ophthalmic lens, which achieves a bestquality image on the retina (instead of slightly in front of the retina)in low lighting conditions.

[0007] Under low lighting conditions, the best quality image of priorart multifocal ophthalmic lenses is not focused on the retina of theeye. Instead, these prior art multifocal ophthalmic lenses have a bestquality image in front of the retina in low lighting conditions, whichcorresponds to a mean power of the multifocal ophthalmic lens beingslightly higher than the far vision correction power required for thepatient.

SUMMARY OF THE INVENTION

[0008] As light diminishes and pupil size correspondingly increases, theouter annular zones of a multifocal ophthalmic lens begin to pass lighttherethrough. These outer annular zones traditionally introduceadditional near vision correction power, which effectively shifts thebest quality image from on the retina to an area slightly in front ofthe retina.

[0009] The outer annular zones of the present invention have visioncorrection powers, which are less than the far vision correction powerof the patient, to compensate for the increase in the mean power of themultifocal ophthalmic lens. A multifocal ophthalmic lens, having outerannular zones with vision correction powers less than a far vision powerof the patient, is disclosed. The additional annular zone or zones comeinto play when the pupil size increases under dim lighting conditions,to thereby compensate for the additional near vision annular zonesintroduced by the enlarged pupil size. The net effect of the additionalnear vision annular zones and the additional annular zones having powerless than the far vision correction power is to focus the best qualityimage onto the retina of the eye, to thereby reduce halo effects andimprove contrast.

[0010] The multifocal ophthalmic lens of the present invention isadapted to be implanted into an eye or to be disposed in a cornea, andhas a baseline diopter power for far vision correction of the patient.The multifocal ophthalmic lens includes a central zone having a meanvision correction power equivalent to or slightly greater than thebaseline diopter power depending upon pupil size, and includes a firstouter zone located radially outwardly of the central zone.

[0011] A second outer zone located radially outwardly of the first outerzone provides vision correction power, that is less than the baselinediopter power. The vision correction power of the second outer zone canbe substantially constant. Light generally does not pass through thesecond outer zone under bright lighting conditions.

[0012] A third outer zone of the multifocal ophthalmic lens comes intoplay in lower lighting conditions, and includes a vision correctionpower greater than the baseline diopter power. A fourth outer zonecircumscribes the third outer zone, and includes a vision correctionpower, that is less than the baseline diopter power. This fourth outerzone passes light in very low lighting conditions, when the pupil issignificantly dilated. The second and fourth outer zones serve to focuslight slightly behind the retina of the eye, to thereby compensate forlight focused in front of the retina of the eye by the first and thirdouter zones, under dim lighting conditions.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013]FIG. 1 is a schematic view illustrating the focusing of light of aprior art multifocal ophthalmic lens onto a retina;

[0014]FIG. 2 is a plan view of an intraocular multifocal ophthalmic lensof the presently preferred embodiment;

[0015]FIG. 3 is a side elevational view of the intraocular multifocalophthalmic lens of the presently preferred embodiment;

[0016]FIG. 4 is a plot of the power of the optic versus distance fromthe optic axis for the intraocular multifocal ophthalmic lens of thepresently preferred embodiment;

[0017]FIG. 5 is a schematic view illustrating the focusing of light ofthe intraocular multifocal ophthalmic lens of the presently preferredembodiment onto a retina.

[0018] These and other aspects of the present invention are apparent inthe following detailed description and claims, particularly whenconsidered in conjunction with the accompanying drawings in which likeparts bear like reference numerals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019]FIGS. 2 and 3 show an intraocular lens 11, which comprises acircular optic 13 and two fixation members 15 and 17. The optic 13 maybe constructed of rigid biocompatible materials, such aspolymethylmethacrylate (PMMA), or flexible, deformable materials, suchas silicone, hydrogel and the like which enable the optic to be rolledor folded for insertion through a small incision into the eye.

[0020] In the presently preferred embodiment, the fixation members 15and 17 are fine hair-like strands or filaments which are attached to theoptic 13 using conventional techniques. The fixation members 15 and 17may be constructed of a suitable polymeric material, such as PMMA orpolypropylene. Alternatively, the fixation members 15 and 17 may beintegral with the optic 13. The optic 13 and the fixation members 15 and17 may be of any desired number and configuration, and theconfigurations illustrated are purely illustrative.

[0021] The optic 13 has a central zone 18, inner and outer annular nearzones 19 and 20, and an annular far zones 21 and 22. In the presentlypreferred embodiment, the central zone 18 is circular, and theperipheries of the annular zones 19-22 are circular. The annular zones19-22 circumscribe the central zone 18, and the zones are contiguous.The zones 19-22 are concentric and coaxial with the optic 13.

[0022] The zones 18-22 are used in describing the vision correctionpower of the optic 13, and they are arbitrarily defined. Thus, theperipheries of the zones 18-22 and the number of zones may be selectedas desired. However to facilitate describing the optic 13, theperipheries of the annular zones 19-22 are considered to be the zerocrossings in FIG. 4. Although the boundaries of the zones 18-22 areindicated by phantom lines in FIG. 2, it should be understood that theoptic 13 has no such lines in any of its surfaces and that these linesconstitute reference lines which define the zones.

[0023] As shown in FIG. 3, the optic 13 has a convex anterior surface 25and a planar posterior surface 27; however, these configurations aremerely illustrative. Although the vision correction power may be placedon either of the surfaces 25 and 27, in the presently preferredembodiment, the anterior surface 25 is appropriately shaped to providethe desired vision correction powers.

[0024]FIG. 4 shows the preferred manner in which the vision correctionpower of the optic 13 varies from the center or optical axis 29 of theoptic 13 to the circular outer periphery 31 of the optic. A preferredpower distribution curve for a corneal inlay may be similar, oridentical, to the curve of FIG. 4.

[0025] In FIG. 4, the vertical or “Y” axis represents the variation indiopter power of the optic 13 from the baseline or far vision correctionpower, and the “X” or horizontal axis shows the distance outwardly fromthe optical axis 29 in millimeters. Thus, the zero-diopter or baselinepower of FIG. 4 is the power required for far vision for a conventionalmono-focal intraocular lens. The power variation shown in FIG. 4 isapplicable to any radial plane passing through the optical axis 29. Inother words, the power at any given radial distance from the opticalaxis 29 is the same.

[0026] The central zone 18 extends from the optical axis 29 to acircular periphery 33, the first annular near zone 19 is considered asextending from the periphery 33 to a circular periphery 34, and theouter annular near zone 20 is considered as extending from a periphery35 to a periphery 36. The negative diopter power of the two zones 21, 22are of less power than required for far vision and may be considered asfar, far vision correction powers. The annular far, far zone 21 extendsbetween the peripheries 34 and 35, and the annular far, far zone 22extends from the periphery 36 radially outwardly to the outer periphery31 of the optic 13. As shown in FIG. 4, the vision correction powercrosses the “X” axis or baseline at the peripheries 33, 34, 35 and 36.

[0027] As shown in FIG. 4, the vision correction power variesprogressively and continuously from a baseline diopter power at theoptical axis 29 to an apex 38 and then decreases continuously andprogressively from the apex 38 back through the baseline diopter powerto a negative diopter power at a point 39. From the point 39, the visioncorrection power increases continuously and progressively through theperiphery 33 into the inner annular near zone 19. Of course, thediopters shown on the ordinate in FIG. 4 are merely exemplary, and theactual correction provided will vary with the prescription needs of thepatient.

[0028] The apex 38 has a vision correction power for intermediatevision. The intermediate vision correction powers may be considered asbeing in a zone 40 which may be between 0.5 and 0.75 diopters from thebaseline diopter power, as presently embodied. The far vision correctionpowers may be considered as lying between the zone 40 and the baselinediopter correction, and the far, far vision correction powers arenegative. The intermediate, far, and far, far powers combine to providea mean power in the central zone 18.

[0029] Within the inner annular near zone 19, the vision correctionpower varies continuously and progressively from the periphery 33 to aplateau 41; and from the plateau 41, the vision correction power variescontinuously and progressively back to the periphery 34 at the baseline.

[0030] In the far, far zone 21 the vision correction power is below thefar zone correction power, and is substantially constant. This visioncorrection power returns to the baseline at the periphery 35.

[0031] In the outer annular near zone 20, the power varies continuouslyand progressively from the periphery 35 to a plateau 45, and returnscontinuously and progressively from the plateau 45 to the baseline atthe periphery 36.

[0032] In the far, far zone 22, the vision correction power issubstantial constant, below the baseline vision correction power. Thesubstantially constant vision correction power of the far, far zone 22is slightly lower than the substantially constant vision correctionpower of the far, far zone 21, as presently embodied. The visioncorrection power of the far, far zone 22 remains negative from theperiphery 36 to the baseline correction power at the outer periphery 31.

[0033] The inner near zone 19 has regions adjacent the peripheries 33and 34 with far vision correction powers and a second region, whichincludes the plateau 41, with near vision correction powers. Similarly,the outer near zone 20 has regions adjacent the peripheries 35 and 36with far vision correction powers and a second region, which includesthe plateau 45, with near vision correction powers. For example, thenear vision powers may be those which are above 2 or 2.5 diopters. The 2to 2.5 diopters correspond to about 20 to 15 inches, respectively, ofworking distance, and this distance corresponds to the beginning of nearactivities. The two far, far vision correction plateaus 42, 43 of thetwo far, far annular zones 21, 22, respectively, preferably comprisediopter powers approximately one fifth of the distance between thebaseline and the plateaus 41, 45, but located below the baseline.

[0034] As shown in FIG. 4, each of these “near” regions has a majorsegment, i.e., the plateaus 41 and 45 in which the near visioncorrection power is substantially constant. The plateau 41, which liesradially inwardly of the plateau 45, has a greater radial dimension thanthe plateau 45. The difference in radial dimension of the plateaus 41and 45 allows these two plateaus to have approximately the same area.

[0035] Only a relatively small portion of the anterior surface 25 (FIG.3) is dedicated to intermediate vision powers. This can be seen by therelatively small radial region which corresponds to the intermediatezone 40 (FIG. 4) and by the rapid change in diopter power between theplateaus 41 and 45 and the baseline diopter axis.

[0036] The diagrammatic view of FIG. 5 shows how the multifocalophthalmic lens 13 of the present invention focuses parallel light ontoa retina 10 of the eye, in dim lighting conditions. The parallel rays 50pass through the central portion 18 of the multifocal ophthalmic lens13, and are focused onto the retina 10. The rays 51 pass through theintermediate focus region 40 of the central zone 18, and are focused inan area between the retina 10 and the multifocal ophthalmic lens 13. Therays 52 pass through the plateau 41 of the near zone 19 and, dependingupon the lighting conditions, pass through the plateaus 42, 43 of thetwo far, far zones 21, 22, and the plateau 45 of the near zone 20. Theserays 52 are focused slightly behind the retina 10. In the presentlypreferred embodiment, the distance at which the rays 52 are focusedbehind the retina 10, is approximately one-fifth of the distance atwhich the rays 51 are focused in front of the retina 10. The combinationof the rays 50, 51, and 52 combine to form a best quality image on theretina 10 in dim lighting conditions.

[0037] While this invention has been described with respect to variousspecific examples and embodiments, it is to be understood that theinvention is not limited thereto and that it can be variously practicedwithin the scope of the following claims.

What is claimed is:
 1. A multifocal ophthalmic lens for providing visioncorrection powers, the multifocal ophthalmic lens being adapted to beimplanted in an eye or to be disposed in a cornea and having a baselinediopter power for far vision correction, the multifocal ophthalmic lenscomprising: a central zone having a vision correction powerapproximately equal to or greater than the baseline diopter power; afirst outer zone located radially outwardly of the central zone andhaving a vision correction power greater than the baseline diopterpower; and a second outer zone located radially outwardly of the firstouter zone and having mean diopter power, which is less than thebaseline diopter power.
 2. The multifocal ophthalmic lens according toclaim 1 , wherein the central zone has a progressive power region inwhich the vision correction powers vary progressively and in radiallyoutwardly extending order from a far vision correction power, to anintermediate vision correction power, to a far vision correction power,and then to a diopter power which is less than the baseline diopterpower.
 3. The multifocal ophthalmic lens according to claim 2 , whereinthe first outer zone is contiguous with the central zone and has a farvision correction power adjacent the central zone and a region having anear vision correction power, the vision correction power of the firstouter zone between the far and near vision correction powers beingprogressive.
 4. The multifocal ophthalmic lens according to claim 3 ,wherein the first outer zone is annular and circumscribes the centralzone.
 5. The multifocal ophthalmic lens according to claim 4 , furthercomprising a third outer zone circumscribing the second outer zone, andwherein the third outer zone is contiguous with the second outer zoneand has a far vision correction power adjacent the second outer zone anda region having a near vision correction power, the vision correctionpower of the third outer zone between the far and near vision correctionpowers being progressive.
 6. The multifocal ophthalmic lens according toclaim 5 , further comprising a fourth outer zone circumscribing thethird outer zone, and wherein the fourth outer zone has a substantiallyconstant vision correction power, which is less than the baselinediopter power.
 7. The multifocal ophthalmic lens according to claim 6 ,wherein a mean vision correction power of the multifocal ophthalmic lensis approximately equal to the baseline diopter power.
 8. The multifocalophthalmic lens according to claim 7 , wherein the near visioncorrection power of the first outer zone is approximately equal inmagnitude to the near vision correction power of the third outer zone.9. A multifocal ophthalmic lens for providing vision correction power,the multifocal ophthalmic lens being adapted to be implanted in an eyeor to be disposed in a cornea and having a baseline diopter power forfar vision correction, the multifocal ophthalmic lens comprising: anoptical axis; a first annular zone located radially outwardly of theoptical axis and having a vision correction power greater than thebaseline diopter power; and a second annular zone located radiallyoutwardly of the first annular zone and having a substantially constantvision correction power, which is less than the baseline diopter power.10. The multifocal ophthalmic lens according to claim 9 , wherein thefirst annular zone has a far vision correction power and a near visioncorrection power, the vision correction power of the first outer zonebetween the far and near vision correction powers being progressive. 11.The multifocal ophthalmic lens according to claim 10 , wherein thesecond annular zone has a far vision correction power in addition to thesubstantially constant vision correction power, the vision correctionpower of the second annular zone between the far and substantiallyconstant vision correction powers being progressive.
 12. The multifocalophthalmic lens according to claim 11 , wherein the second annular zonecomprises an inner annular far vision correction power, an intermediateannular vision correction power less than the baseline diopter power,and an outer annular far vision correction power.
 13. The multifocalophthalmic lens according to claim 12 , further comprising a thirdannular zone having an inner annular far vision correction power, anintermediate annular near vision correction power, and an outer annularfar vision correction power.
 14. The multifocal ophthalmic lensaccording to claim 13 , further comprising a forth annular zone havingan inner annular far vision correction power, an intermediate annularvision correction power less than the baseline diopter power, and anouter annular far vision correction power.
 15. A multifocal ophthalmiclens for providing vision correction power, the multifocal ophthalmiclens being adapted to be implanted in an eye or to be disposed in acornea, and comprising: a first annular zone having a near visioncorrection power; and a second annular zone circumscribing the firstannular zone and having a substantially constant vision correctionpower, which is less than a far vision correction power.
 16. Amultifocal ophthalmic lens for providing vision correction power andadapted to be implanted in an eye or to be disposed in a cornea, themultifocal ophthalmic lens comprising: a central zone having a visualcorrection power, which is greater than a baseline diopter of themultifocal ophthalmic lens; and an annular zone circumscribing thecentral zone and having a substantially constant vision correctionpower, which is less than the baseline diopter power.
 17. A multifocalophthalmic lens for providing vision correction power and adapted to beimplanted in an eye or to be disposed in a cornea, the multifocalophthalmic lens comprising: a central zone having a visual correctionpower for focusing light a first distance in front of a retina of theeye; and an annular zone circumscribing the central zone for focusinglight approximately 20% of the first distance behind the retina of theeye.
 18. The multifocal ophthalmic lens according to claim 17 , whereinlight passes through the annular zone and is focused, approximately 20%of the first distance behind the retina of the eye, in dim lightingconditions.
 19. A multifocal ophthalmic lens for providing visioncorrection power, the multifocal ophthalmic lens being adapted to beimplanted in an eye or to be disposed in a cornea, and comprising: afirst annular zone with a near vision correction power; a second annularzone, circumscribing the first annular zone, with a vision correctionpower that is less than a far vision correction power; and a thirdannular zone, circumscribing the second annular zone, with a near visioncorrection power having a magnitude approximately equal to a magnitudeof the near vision correction of the first annular zone.
 20. Themultifocal ophthalmic lens according to claim 19 , wherein the magnitudeof the near vision correction power of the first annular zone, relativeto the far vision correction power, is approximately five times amagnitude of the vision correction power of the second annular zone,relative to the far vision correction power.